The eye gear must be designated ISO 12312-2, meaning they meet the eye protection requirements for the direct observation of the sun.

Regular sunglasses do not provide enough protection, since they don't block out the ultra-violet and infrared rays that can damage the eyes.

Counterfeit eclipse glasses have raised safety concerns recently and NASA is warning eclipse-gazers to look for products with an “ISO” icon and the company name and contact information clearly printed on the glasses.

They also suggest inspecting the solar filter lenses for scratches or damage before use.

Ralph Chou, professor with School of Optometry & Vision Science at the University of Waterloo, told space.com even the “tiniest sliver of a crescent sun peeking out from behind the moon emits enough light to scorch your eyes.

"I have seen instances where the patient has eventually shown up with crescents burned into the back of the eye, and you can almost tell exactly when they looked."